Saturday, November 28, 2009

Von Baer was a Prussian-Estonian embryologist who discovered the mammalian egg (1827) and the notochord. He established the new science of comparative embryology alongside comparative anatomy with the publication of two landmark volumes (in 1828 and 1837) covering the range of existing knowledge of the prebirth developments of vertebrates.

He showed that mammalian eggs were not the follicles of the ovary but microscopic particles inside the follicles. He described the development of the embryo from layers of tissue, which he called germ layers, and demonstrated similarities in the embryos of different species of vertebrates.

Scott was an English paleobotanist and leading authority of his time on the structure of fossil plants, one of those who laid the foundations of paleobotany. He conducted experiments in the Jodrell Laboratory in Kew Gardens, where he became its honorary keeper (1892-1906). In collaboration with W.C. Williamson, he wrote three papers on fossil-plant morphology (1894-95).

Scott continued writing papers after Williamson's death and in which he described many otherwise unknown fossil plants. He wrote the classic Studies in Fossil Botany, which greatly popularized the subject.

Abstract [edit]: Talon size variation among digits can be used to distinguish families of raptors and is related to different techniques of prey restraint and immobilisation.

The hypertrophied talons on digits (D) I and II in Accipitridae have evolved primarily to restrain large struggling prey while they are immobilised by dismemberment.

Falconidae have only modest talons on each digit and only slightly enlarged D-I and II. For immobilisation, Falconini rely more strongly on strike impact and breaking the necks of their prey, having evolved a ‘tooth’ on the beak to aid in doing so.

Pandionidae have enlarged, highly recurved talons on each digit, an adaptation for piscivory, convergently seen to a lesser extent in fishing eagles.

Strigiformes bear enlarged talons with comparatively low curvature on each digit, part of a suite of adaptations to increase constriction efficiency by maximising grip strength, indicative of specialisation on small prey.

Restraint and immobilisation strategy change as prey increase in size. Small prey are restrained by containment within the foot and immobilised by constriction and beak attacks. Large prey are restrained by pinning under the bodyweight of the raptor, maintaining grip with the talons, and immobilised by dismemberment (Accipitridae), or severing the spinal cord (Falconini).

Within all raptors, physical attributes of the feet trade off against each other to attain great strength, but it is the variable means by which this is achieved that distinguishes them ecologically.

“[The blog] will encompass a wide range of topics, spanning paleontology, evolution, ecology, education, sustainability, philosophy, and psychology. The thread that I will use to weave these topics together is science education in general, and nature literacy more specifically. My underlying contention (shared by growing numbers of people from all walks of life) is that the current sustainability crisis is not merely an external crisis of the environment. More fundamentally, it is an internal crisis of worldview rooted in a dysfunctional relationship between humans and nonhuman nature. Thus, any meaningful resolution to the eco-crisis will require not only more and “greener” technologies, but also a fundamental shift in awareness and understanding, particularly within industrialized nations.

“… I am convinced that the concept of evolution has a pivotal role to play in this gargantuan effort. Darwin triggered an intellectual revolution, with effects that have cascaded through science and society. Yet, one hundred and fifty years later, a portion of Darwin’s legacy, the foundational concept of common descent through deep time, remains virtually untapped outside academia. In particular, this concept has not been communicated in such a way as to shift our relationship with nature.

Schooling for sustainability, I will contend, should be rooted in three intertwined elements, each of which informs the other two: 1) new metaphors that augment the dominant “life-as-machine” and “web of life examples, enabling us to perceive reality in new and instructive ways; 2) the Great Story (encompassing the evolution of cosmos, life, and culture), which provides a universal origin myth and anchors us in the deep time evolution of life on Earth; and 3) a strong emphasis on place. Together, this trio of elements—metaphor, story, and place—have the power to transform education and help trigger a change in the dominant worldview, thereby serving as springboard to a sustainable future.”

Tuesday, November 24, 2009

In 1859, The Origin of Species by Means of Natural Selection was published in England to great acclaim. In this groundbreaking book by British naturalist Charles Darwin, he argued that species are the result of a gradual biological evolution in which nature encourages, through natural selection, the propagation of those species best suited to their environments. This book is unquestionably one of the most influential in the history of science.

Monday, November 23, 2009

In 2003 Australian and Indonesian scientists discovered small-bodied, small-brained, hominin (human-like) fossils on the remote island of Flores in the Indonesian archipelago. This discovery of a new human species called Homo floresiensis has spawned much debate with some researchers claiming that the small creatures are really modern humans whose tiny head and brain are the result of a medical condition called microcephaly.

Researchers have confirmed that Homo floresiensis is a genuine ancient human species and not a descendant of healthy humans dwarfed by disease. Using statistical analysis on skeletal remains of a well-preserved female specimen, researchers determined the "hobbit" to be a distinct species and not a genetically flawed version of modern humans.

The cranial capacity of LB1 was just over 400 cm, making it more similar to the brains of a chimpanzee or bipedal "ape-men" of East and South Africa. The skull and jawbone features are much more primitive looking than any normal modern human. Statistical analysis of skull shapes show modern humans cluster together in one group, microcephalic humans in another and the hobbit along with ancient hominins in a third.

Friday, November 20, 2009

Dawson was a Canadian geologist who made numerous contributions to paleobotany and extended the knowledge of Canadian geology. Dawson was born and raised in Pictou, Nova Scotia, where the many sandstone and coal formations provided fertile ground for his first scientific explorations, which culminated in the publication of Acadian Geology. He made many important discoveries of fossil life, great and small. These included fossil plants, trackways of lowly invertebrates, footprints, skeletons of reptiles and amphibians, millipedes and the earliest land snails. When the famous geologist Charles Lyell visited coal deposits in Pictou, Dawson acted as his guide.

In 1851, Dawson and Lyell teamed up again to examine the interiors of fossil tree trunks at Joggins, Nova Scotia. They discovered the remains of some of the earliest known reptiles, Hylonomus lyelli, along with other rare fossils, propelling this part of the world into the international spotlight.

Dawson became principal of McGill College in Montreal in 1854, which he made into a reputable institution. He remained there, teaching geology and palaeontology and acting as librarian, until his retirement. One of his lifelong dreams was realized in 1882 when Peter Redpath gave money to McGill for the construction and establishment of a museum, naming Dawson as director. Today the Peter Redpath Museum of Natural History houses many specimens from Dawson's personal collection.

Tuesday, November 17, 2009

The Ghost of Slumber Mountain was written and directed by special effects pioneer Willis O'Brien and produced by Herbert M. Dawley. When O’Brien went on to greater fame with The Lost World Dawley sued the film makers for patent infrigment, claiming that he, not O’Brien, had invented stop-motion animation. Although this was not the case, filming saw head up while the case was sorted out.

Both O’Brien and Hawley star as the ghost of Mad Dick and Uncle Jack Holmes, respectively.

A handout photo taken by Japanese researchers of Aquamarine Fukushima aquarium in October shows a juvenile coelacanth. Japanese marine researchers have said they found and successfully filmed a young coelacanth -- a rare type of fish known as "a living fossil" -- in deep water off Indonesia. link

Four different types of conodont teeth from different species.Photo: U of Leicester

Earth's oceans teemed with conodonts for 300 million years; they were the most common vertebrates around, and they were the first to evolve teeth. In fact the conodont skeleton was all teeth: a basket of hacksaw-shaped blades which was extended out of the mouth to grab prey, behind which lay pairs of slicing blades and crushing teeth.

Ancient marine rocks are often packed with thousands of scattered microscopic conodont teeth, with many species jumbled up together. To make matters worse, within any one animal, teeth from different parts of the skeleton looked almost identical!

To help sort out the problem scientists studied material from a 425 million year old rock deposit in Ontario, Canada which, unlike almost all other deposits in the world, preserves both scattered teeth and complete skeletons of conodonts. This material allowed them to compare the success rate of experts in placing the teeth in the correct positions within the skeleton, with the success rate of computer-based methods.

So how do the experts stack up against the machines?

"Pretty well" says Jones. "This is reassuring for palaeontologists! but the computer-based approach did at least as well and was also consistent.

Abstract: The importance of the centre of percussion (CP) of some hand-held sporting equipment (such as tennis rackets and baseball bats) for athletic performance is well known. In order to avoid injuries it is important that powerful blows are located close to the CP.

Several species of glyptodont (giant armoured mammals) had tail clubs that can be modelled as rigid beams (like baseball bats) and it is generally assumed that these were useful for agonistic behaviour. However, the variation in tail club morphology among known genera suggests that a biomechanical and functional analysis of these structures could be useful.

Here, we outline a novel method to determine the CP of the glyptodont tail clubs. We find that the largest species had the CP very close to the possible location of horny spikes. This is consistent with the inference that they were adapted to delivering powerful blows at that point. Our new analysis reinforces the case for agonistic use of tail clubs in several glyptodont species.

Review: The author has taken the traditional approach of most dinosaur books that discusses each group chapter by chapter and turned it on its ear. In Dinosaur Odyssey Sampson is more concerned with what dinosaurs can teach us about the evolution of the Earth and our place in the intricate web of life than about any specific specimen of T. rex or Triceratops. Scott weaves an engaging story of the history of Earth and takes entire chapters to explain topics like the energy cycle and the soil formation, all the time relating these seemingly mundane topics back to why they are intimately involved with dinosaurs as living animals. And that’s where this book excels – making the dinosaurs and their world come alive while at the same time making the reader understand that the same processes that shaped the dinosaurs and their ecology also shapes ours today. Although the dinosaur’s extinction (except birds!) was caused by outside forces, the one staring us squarely in the eye is self-imposed. In many ways this book will, I suspect, act as a jumping off point for Scott’s long term commitment surrounding education and sustainability.

Scott touches on the major advances in dinosaur palaeobiology and uses these to discuss at length his (developed with Jim Farlow) concept of ‘mesothermy’ to explain the success of the dinosaurs, especially the gigantic sauropods. In this ‘Goldilocks’ hypothesis dinosaur were not quite endotherms and not quite ectotherms, but something in between that that gave them the benefits of each type of physiology while minimizing their disadvantages. As a hypothesis this is fine but I still want to read the scientific paper that presents this concept in detail!

The real strength of this book is Scott’s ease at weaving sometimes dry or complicated topics into an engaging narrative that brings dinosaurs alive, and the book often works best when Scott is relating events that he was directly involved in. I’m hoping that he (or some member of the crew) will write a book about the work and adventures of collecting dinosaurs in Madagascar.

The book is sparsely illustrated with an eight page colour insert, and a colour cover & evocative pencil illustrations by Michael Skrepnick that introduce each chapter.

This book is written for someone with at least a high school understanding of biology and is, in a sense, an updated version of Bob Bakker’s Dinosaur Heresies for a new generation of palaeo-enthusiasts and palaeontologists to be. For the kids and their parents who know Scott as the host of the highly successful “Dinosaur Train”, here’s hoping that he writes a version of this book for the little ones.

Finally, I have to divulge that Scott is an old friend of mine and at one time our research interests strongly overlapped. Those of you who know Scott for his charismatic speaking skills will be pleased to know that his passion also comes through in his writing.

Recommendation: Highly recommended.

PS. Scott Sampson will be speaking and signing copies of Dinosaur Odyssey at the Cleveland Museum of Natural History this January as part of our Explorer Speaker series. More info here.

Review: The Great Dinosaur Discoveries is another in the very long line of highly illustrated, general dinosaur books that line the sale walls at your local box mall bookstore. I was prepared to write it off without even looking at it, but once I opened it I was interested enough to read it through to the end (it’s a quick read).

What sets this book ahead of the rest of the pack is its design and layout that groups most items under discussion into well-arranged, double-paged spreads with well written text and well chosen photos or illustrations.

The book divides the dinosaurs under discussion into their various historical eras of discovery, but manages to make the story of Mantell’s description of Iguanodon (1825) as colourful and interesting as that of Eotriceratops (2007). I liked the short appendix listing key figures in dinosaur palaeontology.

This book is designed for anyone interested in dinosaurs but will probably be most favoured by the pre-high school reader who has not already devoured the more dinosaur academic texts. It’s the perfect book to recommend to someone who is looking for a general book on dinosaurs for their kids. I can see myself grabbing this book off the shelf for a quick fact check or an image for a talk.

Saturday, November 14, 2009

Sir Charles Lyell attended Oxford University at age 19. Lyell's father was an active naturalist. Lyell had access to an elaborate library including subjects such as Geology.

When Lyell was at Oxford, his interests were mathematics, classics, law and geology. He attended a lecture by William Buckland that triggered his enthusiasm for geology. Lyell originally started his career as a lawyer, but later turned to geology. He became an author of The Geological Evidence of the Antiquity of Man in 1863 and Principles of Geology. Lyell argued in this book that, at the time, presently observable geological processes were adequate to explain geological history. He thought the action of the rain, sea, volcanoes and earthquakes explained the geological history of more ancient times.

Lyell rebelled against the prevailing theories of geology of the time. He thought the theories were biased, based on the interpretation of Genesis. He thought it would be more practical to exclude sudden geological catastrophes to vouch for fossil remains of extinct species and believed it was necessary to create a vast time scale for Earth's history. This concept was called Uniformitarianism. The second edition of Principles of Geology introduced new ideas regarding metamorphic rocks. It described rock changes due to high temperature in sedimentary rocks adjacent to igneous rocks. His third volume dealt with paleontology and stratigraphy. Lyell stressed that the antiquity of human species was far beyond the accepted theories of that time.

Charles Darwin became his dear friend and correspondent. Darwin is quoted saying, "The greatest merit of the Principles was that it altered the whole tone of one's mind, and therefore that, when seeing a thing never seen by Lyell, one yet saw it through his eyes."

Thursday, November 12, 2009

Title: Evolution: The Story of LifeAuthor: Douglas Palmer; with illustrations by Peter BarrettPublishing Information: University of California Press, HC, 374 pages, November 9, 2009, $39.95Ordering Numbers: ISBN-10: 0520255119; ISBN-13: 978-0520255111Review copy: complimentaryFrom the Publisher: Evolution recreates the 3.5-billion-year story of life on Earth in stunning detail through vivid full-color illustrations and graphics, the latest scientific information, and hundreds of photographs. At the heart of the book is an astonishing, beautifully detailed panorama by renowned illustrator Peter Barrett that, in 100 double-page site reconstructions, offers a freeze-frame view of the communities. These groundbreaking artworks, based on the most recent findings at some of the most famous fossil sites around the world, are paired with an authoritative and highly informative text written for a wide audience of readers.

Review: One of the most frequent questions I get as a palaeontologist is “what did prehistoric locality ‘X’ look like when its fossils were alive?" This book answers that in the 100 double spread reconstructions of 100 famous (or important) fossil localities from around the world. Each panorama provides a synthesize of the environment including important flora and fauna, with concise inserts providing more details on time, place, taxa and other notable facts. The results are truly stunning and will give both the casual fossil enthusiast and jaded professionals new insights into each important evolutionary time slice.

The reconstructions are supplemented by a 45 page examination of the evolutionary ‘tree of life’, a 21 page “Site Gazetteer” with more info and references on the localities depicted in the book, 29 pages of info on the species covered in the book, and finally a fold out that stitches all of the panoramas together.

This prodigious work is recommended, but there is at least one caveat to add. Many of the panoramas average together large regions leading to some factual errors on closer examination, e.g. the Dinosaurs of “Cretaceous Park” (p. 174-5) implies that it covers the Judith River Formation of Montana and Alberta but it actually just covers the Dinosaur Park Formation of Alberta. There are no Chasmosaurus specimens known from Montana, and the Judith River Formation of Canada is not known as the Belly River Formation in Canada (there is no Belly River Formation). The only reference for this region (the excellent Dinosaur Provincial Park edited by Currie and Koppelhus) misspells the second author’s name. And, although many important fossils have been collected from Ukhaa Tolgod in Mongolia, the famous fighting dinosaurs (P. 172) are actually from Togrogiin Shiree. Hopefully these minor problems can be corrected for the 2nd edition.

Early life on Earth may have developed more quickly than previously thought.

The Earth's climate was far cooler – perhaps more than 50 degrees – billions of years ago. That means that conditions for life were much easier, and that life that did exist at the time was not under as much stress as previously believed.

The team examined rocks from the Buck Reef Chert in South Africa that are known to be about 3.4 billion years old, among the oldest ever discovered. They found features in them that are consistent with formation at water temperatures significantly lower than previous studies had suggested.

"Our research shows that the water temperature 3.4 billion years ago was at most 105 degrees, and while that's potentially very warm, it's far below the temperatures of 155 degrees or more that previous research has implied," Tice explains.

The situation could be compared to the geysers currently found in Yellowstone National Park. The hundreds of hot spring pools in the park vary considerably in temperature but the water in the pools that is farthest from the center is cooler.

When water temperatures fall to below 163 degrees or so, close to the high temperatures previously hypothesized for the early ocean, communities of green photosynthetic bacteria begin to grow on the pool floor. These communities become thicker as water temperature continues to drop off away from the pool centers.

"There is life even in the hottest water, and microbes there have evolved to grow in those harsh conditions. But there is even more life present in the cooler waters," he notes. "We think this is similar to what conditions might have been like billions of years ago." link

Abstract [edit]: gen. et sp. nov. is described from the upper Elliot Formation (Early Jurassic) of South Africa. It is found to be the sister group of a clade of obligatory quadrupedal sauropodomorphs (Melanorosaurus + Sauropoda) and thus lies at the heart of the basal sauropodomorph–sauropod transition.

The narrow jaws of A. celestae retain a pointed symphysis but appear to have lacked fleshy cheeks. Broad, U-shaped jaws were previously thought to have evolved prior to the loss of gape-restricting cheeks. However, the narrow jaws of A. celestae retain a pointed symphysis but appear to have lacked fleshy cheeks, demonstrating unappreciated homoplasy in the evolution of the sauropod bulk-browsing apparatus.

The limbs of A. celestae indicate that it retained a habitual bipedal gait although incipient characters associated with the pronation of the manus and the adoption of a quadrupedal gait are evident through geometric morphometric analysis (using thin-plate splines) of the ulna and femur. Cursorial ability appears to have been reduced and the weight bearing axis of the pes shifted to a medial, entaxonic position, falsifying the hypothesis that entaxony evolved in sauropods only after an obligate quadrupedal gait had been adopted.

Wednesday, November 11, 2009

Novel research on locomotion shows that the earliest dinosaurs may have been warm-blooded.

Studies of present-day animals have shown that endothermic animals are able to sustain much higher rates of energy use. Following from this, if the energy cost of walking and running could be estimated in dinosaurs, the results might show whether these extinct species were warm- or cold-blooded. If walking and running burned more energy than a cold-blooded physiology can supply, these dinosaurs were probably warm-blooded.

But metabolism and energy use are complex biological processes, and all that remains of extinct dinosaurs are their bones. So, the authors made use of a recent work by Pontzer showing that the energy cost of walking and running is strongly associated with leg length – so much so that hip height (the distance from the hip joint to the ground) can predict the observed cost of locomotion with 98% accuracy for a wide variety of land animals. As hip height can be simply estimated from the length of fossilized leg bones, Pontzer and colleagues were able to use this to obtain simple but reliable estimates of locomotor cost for dinosaurs.

To back up these estimates, the authors used a more complex method based on estimating the actual volume of leg muscle dinosaurs would have had to activate in order to move, using methods Hutchinson and Pontzer had previously developed. Activating more muscle leads to greater energy demands, which may in turn require an endothermic metabolism to fuel.

Click to enlarge

Results suggest that based on the energy they consumed when moving, many dinosaurs were probably endothermic, athletic animals because their energy requirements during walking and running were too high for cold-blooded animals to produce. Interestingly, when the results for each dinosaur were arranged into an evolutionary family tree (above), the authors found that endothermy might be the ancestral condition for all dinosaurs.

This early adoption of high metabolic rates may be one of the key factors in the massive evolutionary success that dinosaurs enjoyed during the Triassic, Jurassic and Cretaceous periods, and continue to enjoy now in feathery, flying form.link

The scientists claim that their discovery is unequivocal evidence that high-fidelity organic preservation of extremely decay prone soft tissues is more common in the fossil record – the only physical record of the history of life on earth.

Previous examples of soft tissues fossilised in this way have been limited to samples extracted from amber or inside bone – a very rare set of circumstances. This latest discovery simply occurs inside the body of the salamander tucked in beside the spine.

“We came across the muscle tissue during our analysis of several hundred fossil samples taken from an ancient lake bed in Southern Spain. It was immediately identifiable by the sinewy texture visible under the microscope,” says Dr Patrick Orr.

”We noticed that there had been very little degradation since it was originally fossilised about 18 million years ago, making it the highest quality soft tissue preservation ever documented in the fossil record.” The muscle tissue is organically preserved in three dimensions, with circulatory vessels infilled with blood. link

Balfour (Nov. 10, 1851 – July 19, 1882) was a British zoologist and a founder of modern embryology. Influenced by the work of Michael Foster, with whom he wrote Elements of Embryology (1883), Balfour showed the evolutionary connection between vertebrates and certain invertebrates (similar to research being done by Aleksandr Kovalevski).

Balfour proposed the term Chordata for all animals possessing a notochord at some stage in their development. He also did pioneer work on the development of the kidneys and related organs, as well as the spinal nervous system. While convalescing from typhoid fever in Switzerland, he died at the young age of 30 from a fall while attempting an ascent of the unconquered Aiguille Blanche of Mont Blanc. From Today In Science History

Mantell (Feb. 3, 1790 – Nov. 10, 1852), a physician of Lewes in Sussex in southern England, had for years been collecting fossils in the sandstone of Tilgate forest, and he had discovered bones belonging to three extinct species: a giant crocodile, a plesiosaur, and Buckland's Megalosaurus. But in 1822 he found several teeth that "possessed characters so remarkable" that they had to have come from a fourth and distinct species of Saurian. After consulting numerous experts, Mantell finally recognized that the teeth bore an uncanny resemblance to the teeth of the living iguana, except that they were twenty times larger. In this paper, the second published description of a dinosaur, he concluded that he had found the teeth of a giant lizard, which he named Iguanodon, or "Iguana-tooth."

Mantell illustrated his announcement with a single lithographed plate. Mantell included at the bottom of the plate a drawing of a recent iguana jaw, which is shown four times natural size, and for further comparison, he added views of the inner and outer surface of a single iguana tooth, "greatly magnified."

The traditional story that Mantell's wife found the first teeth in 1822, while the doctor was visiting a patient, appears, alas, to be unfounded.

Monday, November 09, 2009

Kovalevsky (Nov. 7, 1840 – Nov. 9, 1901) was the Russian founder of comparative embryology and experimental histology, who first established that there was a common pattern in the embryological development of all multicellular animals. He studied the lancelet, a 5 cm long fish-shaped sea animal. He then wrote Development of Amphioxuslanceolatus (1865).

In 1866, he then demonstrated the similarity between Amphioxus [=Branchiostoma] and the larval stages of tunicates and established the chordate status of the tunicates.

In 1867, Kovalevsky extended the germ layer concept of Christian Heinrich Pander and Karl Ernst von Baer to include the invertebrates, establishing an important embryologic unity in the animal kingdom.imageFrom Today In Science History

Padian explores some common inaccuracies and untruths about Darwin and his life's work, painting in the process a clear portrait of the man and his struggles to develop a theory to explain the diversity of nature.

Costa draws on Darwin's letters and notebooks and other sources to trace the origins of Darwin's key insights, which came to him over many years. Costa suggests that biology teachers can use Darwin's reasoning as a superb example of creative scientific thinking.

Saturday, November 07, 2009

Abstract: The head and mouthpart structures of 11 species of Eurasian scorpionflies represent three extinct and closely related families during a 62-million-year interval from the late Middle Jurassic to the late Early Cretaceous. These taxa had elongate, siphonate (tubular) proboscides and fed on ovular secretions of extinct gymnosperms. Five potential ovulate host-plant taxa co-occur with these insects: a seed fern, conifer, ginkgoopsid, pentoxylalean, and gnetalean

The presence of scorpionfly taxa suggests that siphonate proboscides fed on gymnosperm pollination drops and likely engaged in pollination mutualisms with gymnosperms during the mid-Mesozoic, long before the similar and independent coevolution of nectar-feeding flies, moths, and beetles on angiosperms. All three scorpionfly families became extinct during the later Early Cretaceous, coincident with global gymnosperm-to-angiosperm turnover.

Wallace (Jan. 8, 1823 – Nov. 7, 1913) was a British naturalist and biogeographer. He was the first westerner to describe some of the most interesting natural habitats in the tropics. He is best known for devising a theory of the origin of species through natural selection made independently of Darwin.

Between 1854 and 1862, Wallace assembled evidence of natural selection in the Malay Archipelago, sending his conclusions to Darwin in England. Their findings were jointly presented to the Linnaean Society in 1858. Wallace found that Australian species were more primitive, in evolutionary terms, than those of Asia, and that this reflected the stage at which the two continents had become separated. He proposed an imaginary line (now known as Wallace's line) dividing the fauna of the two regions.

Friday, November 06, 2009

Scientists find a population of butterflies that appears to be splitting into 2 species.

Polymorphic mimicry in Heliconius cydno alithea in western Ecuador, where the white form mimics the white species Heliconius sapho and the yellow form mimics the yellow species Heliconius eleuchia.Credit: M. Kronforst & K. Kunte

Researchers have investigated the relationship between diverging color patterns in Heliconius butterflies and the long-term divergence of populations into new and distinct species.

Heliconius butterflies display incredible color pattern variation across Central and South America, with closely related species usually sporting different colors. In Costa Rica, for example, the two most closely related species differ in color: One species is white and the other is yellow. In addition, both species display a marked preference to mate with butter-flies of the same color.

The Ecuadorian population examined by Kronforst and his colleagues shows the same white and yellow variation found in Costa Rica but has not yet reached a level of strong reproductive isolation. The entire population lives in close proximity and individuals of both colors come in contact with – and mate with – each other.

But, by studying the Ecuadorian population in captivity, the scientists found the two colors do not mate randomly. Despite the genetic similarity between the groups – white and yellow varieties differ only at the color-determining gene – yellow Ecuadorian individuals show a preference for those of the same color. White male butterflies, most of which are heterozygous at the gene that controls color, show no color preference.

"This subtle difference in mate preference between the color forms in Ecuador may be the first step in a process that could eventually result in two species, as we see in Costa Rica," says Kronforst. link

Although male American lions were considerably larger than females, male and female sabertoothed cats are indistinguishable in size. This suggests that sabertooths may have been less aggressive than their fellow felines.

ABSTRACT: Sexual dimorphism has long been purported in the American lion Panthera atrox well-known from the asphalt deposits at Rancho La Brea. However, few studies have quantified this dimorphism. Along with the sabertoothed cat, Smilodon fatalis, we examine sexual dimorphism in dentaries from the Rancho La Brea tar pits using extant Panthera leo as a guide. Although growth rate in large carnivores declines after a certain age, it has been demonstrated to continue well beyond adulthood, therefore age must also be incorporated into a measure of sexual dimorphism in large carnivores. Prior studies demonstrated that tooth wear can be an inaccurate measure of age in Rancho La Brean carnivores, as it is affected by both diet and age.

This study, instead, uses per cent pulp cavity closure of the lower canine tooth which is solely a measure of relative age, combined with linear measurements of the dentaries to separate the sexes of these two extinct cats. Results show that P. atrox has similar, or slightly greater, levels of sexual dimorphism than P. leo, whereas S. fatalis shows little to no sexual dimorphism. Our results also demonstrate that both Panthera species continue to grow into adulthood, strengthening the case that it is necessary to incorporate a measure of age into studies of sexual dimorphism in large carnivores, living or extinct.

Osborn graduated at Princeton in 1877 and pursued his interest in the biological sciences and paleontology through additional study at several New York City medical schools and with Thomas Henry Huxley in Britain. Returning to the United States, Osborn accepted a position at Princeton, teaching natural sciences from 1881 until 1891, when he moved to Columbia University to organize the Biology Department there, and in 1891, he also helped to organize the Department of Vertebrate Paleontology at the American Museum of Natural History acting as it’s first curator. Osborn's close association with American Museum continued for over 45 years, and included a long tenure as its President, 1908-1933. During these years the museum's collections expanded enormously and it became one of the preeminent research institutions for natural history in the world.

Osborn is noted for describing and naming both Tyrannosaurus rex and Albertosaurus in 1905, Pentaceratops in 1923, and Velociraptor in 1924. One of Osborn's favorite groups for study was the brontotheres, and he was the first to carry out comprehensive research on them. He also wrote an influential textbook, The Age of Mammals (1910).

Apart from his own research, Osborn is perhaps best remembered for the sponsorship of the five immensely successful Central Asiatic Expeditions during the 1920's and 30's led by Roy Chapman Andrews.

ABSTRACT: The cranial osteology of the small theropod dinosaur Proceratosaurus from the Bathonian of Minchinhampton, England, is described in detail, based on new preparation and computed tomography (CT) scan images of the type, and only known, specimen.

Proceratosaurus is an unusual theropod with markedly enlarged external nares and a cranial crest starting at the premaxillary–nasal junction. The skull is highly pneumatic, with pneumatized nasals, jugals, and maxillae, as well as a highly pneumatic braincase, featuring basisphenoid, anterior tympanic, basipterygoid, and carotid recesses. The dentition is unusual, with small premaxillary teeth and much larger lateral teeth, with a pronounced size difference of the serrations between the mesial and distal carina. The first dentary tooth is somewhat procumbent and flexed anteriorly.

Phylogenetic analysis places Proceratosaurus in the Tyrannosauroidea, in a monophyletic clade Proceratosauridae, together with the Oxfordian Chinese taxon Guanlong. The Bathonian age of Proceratosaurus extends the origin of all clades of basal coelurosaurs back into the Middle Jurassic, and provides evidence for an early, Laurasia-wide, dispersal of the Tyrannosauroidea during the late Middle to Late Jurassic.link

Haldane (Nov. 5, 1892 - Dec. 1, 1964) is best remembered along with E. B. Ford and R. A. Fisher one of the three major figures to develop the mathematical theory of population genetics. His greatest contribution was in a series of ten papers on "A Mathematical Theory of Natural and Artificial Selection" which was the major series of papers on the mathematical theory of natural selection. It treated many major cases for the first time, showing the direction and rates of changes of gene frequencies. It also pioneered in investigating the interaction of natural selection with mutation and with migration.

Haldane's book, The Causes of Evolution (1932), summarized these results, especially in its extensive appendix. This body of work was a component of what came to be known as the "modern evolutionary synthesis", re-establishing natural selection as the premier mechanism of evolution by explaining it in terms of the mathematical consequences of Mendelian genetics. From Wikipedia. More info here.

”Romer was director of the Museum of Comparative Zoology at Harvard University until his retirement in 1961 and was one the singularly most influential vertebrate paleontologists of the 20th Century. His work ranged over virtually every conceivable subject within that field, although it was the osteology and taxonomy of the therapsids and other proto-mammals which was nearest his heart.

In addition to this work, Romer was acutely interested in the origin and initial adaptive radiation of tetrapods, and his work became the basis for a theory of tetrapod origins which was canon until the description of Acanthostega gunnari by Clack & Coates in the 1990s. Romer was ahead of his time in his defense of monophyly of Dinosauria though he did feel that Theropoda was not ancestral to birds.” link from EvoWiki.org

Sunday, November 01, 2009

Abstract [edit]:Dracorex hogwartsia (juvenile) and Stygimoloch spinifer (subadult) are reinterpreted as younger growth stages of Pachycephalosaurus wyomingensis (adult). This synonymy reduces the number of pachycephalosaurid taxa from the Upper Cretaceous of North America and demonstrates the importance of cranial ontogeny in evaluating dinosaur diversity and taxonomy. These growth stages reflect a continuum rather than specific developmental steps defined by “known” terminal morphologies.

The ontogenetically oldest adult, AMNH 1696, in (A) dorsal and (B) right lateral views. A younger adult, UCMP 556078 (cast) with inflation of the frontoparietal dome+lateral cranial elements and mature nasal and squamosal nodal ornamentation in (C) dorsal and (D) right lateral views. MPM 8111, a partial skull of “” in (E) dorsal and (F) left lateral views (reversed) illustrates the high narrow frontoparietal dome, squamosal nodes and horns characteristic of the subadult growth stage. Landmarks on the dorsal skull of MPM 8111 in orange (anterior) and red (posterior) constrain the position of the dome. The youngest growth stage in this cranial ontogenetic series is “Dracorex”, TCNI 2004.17.1 (cast) in (G) dorsal and (H) right lateral views. The position of the squamosal horns and nasal nodes are consistent in these four pachycephalosaurid skulls, which increase in overall length and size from youngest (G,H) to oldest (A,B). Scale bar is 5 cm.

de Beer (Nov. 1, 1899 – June 21, 1972) was an English zoologist and morphologist who contributed to experimental embryology, anatomy, and evolution. He refuted the germ-layer theory and developed the concept of paedomorphism - the retention of juvenile characteristics of ancestors in mature adults).

From examination of the fossil Archaeopteryx, De Beer proposed mosaic evolution with piecemeal evolutionary changes to explain the combination of bird and reptile features.

Alfred Lothar Wegener was a German meteorologist and geophysicist who first gave a well-developed hypothesis of continental drift. He suggested (1912) that about 250 million yrs ago all the present-day continents came from a single primitive land mass, the supercontinent Pangaea, which eventually broke up and gradually drifted apart. (A similar idea was proposed earlier by F.B. Taylor in 1910.) Others saw the fit of coastlines of South America and Africa, but Wegener added more geologic and paleontologic evidence that these two continents were once joined.